Not sure if it's possible on one finger, but if the ecg and afib detection are continuously monitored without having to place an additional finger onto the ring that would be revolutionary. Smart watches cannot do this unless you physically place your finger onto a button or crown of the watch.
Samsung surprisingly hasn't made a continuous ecg even though it could make use of its ring and a Galaxy watch at the same time to enable this. There's your three leads, always monitoring, even when you sleep.
But nah, Samsung would rather have more advanced sleep tracking, just to tell me how poorly I sleep, as if I didn't know already.